Noise-reduced vacuum appliance

ABSTRACT

A vacuum appliance includes a motor having a rotatable shaft. An air flow generating member is connected to the shaft. The air flow generated by the rotating member generates noise having a frequency and corresponding wavelength. An air flow path receives air generated by the rotating member. The air flow path has first and second channels, the lengths of which define a predetermined difference therebetween to cancel the noise. In certain embodiments, the difference is corresponds to one-half wavelength.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional application of U.S. Provisional Application No. 60/594,812, filed on May 9, 2005, which is incorporated by reference.

BACKGROUND

The present invention relates generally to vacuum appliances.

Vacuum appliances are well known. For example, vacuum appliances that are capable of picking up both wet and dry material, commonly referred to as wet/dry vacuums or wet/dry vacs, are often used in workshops and other environments where both wet and dry debris can accumulate. Wet/dry vacuums conventionally consist of a collection canister or drum, usually mounted on a dolly having wheels or casters, and a powerhead within which a motor and impeller assembly is mounted. The motor and impeller assembly creates a suction within the drum, such that debris and/or liquid are drawn into the drum through an air inlet to which a flexible hose can be attached. A filter within the drum prevents incoming debris from escaping from the drum while allowing filtered air to escape.

A typical wet/dry vacuum motor and blower assembly includes a motor having a closed-face, multiple-blade blower wheel or impeller disposed on a drive shaft thereof. The motor and blower assembly is typically disposed in a collection canister lid assembly, with the rotating blower wheel disposed within a blower chamber, sometimes referred to as a collector chamber. The collector chamber is accessed via an air intake, such that a suction created by rotation of the impeller within the collector chamber causes air to be drawn into the air intake.

A conventional wet/dry vacuum has two air flow systems. A first air flow system is established for cooling the motor. The second air flow system is the blower wheel or impeller airflow, which affects the suction performance of the vacuum (and the blowing performance, for those vacs which are adaptable or convertible between and vacuum and a blower).

A common problem with vacuum cleaners, and especially wet/dry vacuums, is the excessive and irritating noise generated by the vacuum cleaner. The vacuum motor itself generates noise, and in vacuum cleaners having blowing ports, the high-velocity air exiting the blowing port further creates an especially annoying high-pitched “whine.” While providing a muffler device on the blowing port and/or adding noise muffling materials inside the appliance is effective at reducing some noise, other components of the appliance continue to contribute to noise production.

The present application addresses shortcomings associated with the prior art.

SUMMARY

In accordance with certain teachings of the present disclosure, a vacuum appliance such as a wet dry vacuum includes a motor having a rotatable shaft. An air flow generating member, such as a blower wheel and/or cooling fan, is connected to the shaft. The air flow generated by the rotating member generates noise having a frequency and corresponding wavelength. In motors having a commutator, such as a universal motor, the rotating commutator further generates air flow and corresponding noise. An air flow path receives air generated by the rotating member. The air flow path has first and second channels, the lengths of which define a predetermined difference therebetween to cancel the noise. In certain embodiments, the difference is corresponds to one-half wavelength.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a block diagram conceptually illustrating portions of a vacuum appliance in accordance with certain teachings of the present disclosure.

FIGS. 2A-2D are graphs illustrating passive noise cancellation effectiveness.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

FIG. 1 is a block diagram conceptually illustrating portions of a vacuum appliance 100 in accordance with certain teachings of the present disclosure. The vacuum 100 includes a collection canister or drum 110 and a powerhead 112 within which a motor and impeller assembly is mounted. The powerhead 112 creates a suction within the drum 110, such that debris and/or liquid are drawn into the drum 110 through an air inlet 114 to which a flexible hose can be attached. A filter 120 within the drum prevents incoming debris from escaping from the drum 110 while allowing filtered air to escape through an air exhaust port (not shown).

The powerhead 112 includes a motor 130 having a blower wheel or impeller 132 disposed on a drive shaft thereof, with the rotating blower wheel disposed within a blower chamber 134, sometimes referred to as a collector chamber. The motor 130 includes a cooling fan 136. A universal motor is used in exemplary vacuum systems. The appliance 100 has two air flow systems. One is established for cooling the motor 130 with the cooling fan 136, and the other is the blower wheel 132 or impeller airflow which generates the suction inside the drum 110.

As noted in the background section herein, it is desirable to continue to reduce noise generated by vacuum appliances such as wet/dry vacuums. Sources of noise generated by the powerhead include the blower wheel 132, the motor's commutator/brush interface, and the cooling fan 136. By manipulating passageways for the motor cooling air 150 and the motor exhaust air 152 such that the length of the passageway corresponds to wavelengths of noise frequencies to be eliminated, the overall noise level of the appliance is reduced without the addition of noise-reducing hardware. The passageways 150,152 are created so that the wavelengths are 180 degrees out of phase for the particular frequency to be eliminated.

In one exemplary implementation, dual air channels were provided in a wet/dry vacuum for each of three noise sources, with corresponding frequency (cycles/second) and wavelength (inches):

Blower wheel: 2,333,3 cycles/sec; 5.80 inches

Cooling Fan: 3,666,7 cycles/sec; 3.69 inches

Commutator: 7,333.3 cycles/sec; 1.85 inches.

The channels of the dual air channels corresponding to each of these noise sources is one-half wavelength different in length, so one channel “cancels” the noise of the other channel.

FIGS. 2A-2D are graphs illustrating motor frequency, frequency with commutator cancellation, frequency with cooling fan cancellation and frequency with both commutator and cooling fan cancellation, respectively. As shown in the graphs, substantial noise reduction is achieved with both commutator and cooling fan cancellation.

In tests where the difference between the two flow length paths for the various air channels was varied, the noise level was minimal when the difference between flow length channels was one-half wavelength. In contrast, the noise level was maximum when the difference between the flow length channels was one-quarter wavelength, because at this difference, the noise is additive and not canceling.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. 

1. A vacuum appliance, comprising: a motor having a rotatable shaft; an air flow generating member connected to the shaft, the air flow generating member generating noise having a frequency and corresponding wavelength; and an air flow path receiving air generated by the air flow generating member, the air flow path including first and second channels, each channel defining corresponding first and second lengths, the first and second lengths defining a predetermined difference therebetween to cancel the noise.
 2. The vacuum appliance of claim 1, wherein the predetermined difference between the first and second lengths corresponds to one-half wavelength.
 3. The vacuum appliance of claim 1, wherein the air flow generating member comprises a blower wheel.
 4. The vacuum appliance of claim 1, wherein the air flow generating member comprises a cooling fan.
 5. The vacuum appliance of claim 1, wherein the air flow generating member comprises a commutator of the motor. 